Method for controlling a cooking process, and cooking appliance

ABSTRACT

A cooking appliance and a method of controlling the cooking process in the cooking appliance. The cooking appliance includes a heating device, especially for grilling. To improve the browning process of food in the cooking appliance the radiation time of the cooking appliance is increased. The time is increased by a temporary cooling-down phase where the temperature is reduced, that is initiated by opening the cooking appliance door, for example, to turn the food being browned. The cooking appliance then increases the temperature again over a subsequent heating-up phase initiated by closing the cooking appliance door.

The invention relates to a method for controlling a cooking process andto a cooking device of the type explained in the preambles of claims 1and 6.

Cooking devices in the form of cookers or the like are known in largenumbers. The cooking process in these cooking devices is usuallycontrolled by the user selecting manually either a certain cookingtemperature or a certain pre-determined operating mode (and optionallyan operating time) to which a certain cooking temperature isautomatically allocated. When this cooking temperature is reached, thecooking temperature is then substantially held constant within atemperature regulating cycle, the heating device being switched on andoff when a pre-determined temperature is reached in each case, whereinthe temperature usually oscillates within a temperature range.

In shorter operating modes, such as the “grilling” operating mode,however there is the problem that the browning of the food is frequentlyunsatisfactory. In these shorter operating modes the degree of browningof the food depends on the time during which the food is exposed todirect thermal irradiation by the switched-on heating device. In thepre-heating phase the heating device is switched on continuously so thatthe food is continuously exposed to thermal radiation and thus brownswell. During the regulating cycle however, the heating device isswitched off cyclically so that the food is exposed to thermalconvection in addition to the browning thermal radiation, as a result ofwhich the food is browned less well. This is particularly noticeablewhen the food needs to be turned in the course of the cooking process,where the first side is then well-browned but the second side is rathercooked and less well browned.

It is the object of the invention to provide a method and a cookingdevice which provides a better browning result.

The invention is solved by a method according to claim 1 and a cookingdevice according to claim 6.

The proposal according to the invention to reduce the temperature overthe course of a temporary cooling-down phase during the cooking processhas the effect that the heating device then remains switched on for alonger time so that the food is exposed to the browning thermalradiation for a longer time.

Advantageous further developments of the invention can be deduced fromthe dependent claims.

It is particularly appropriate if the temporary cooling-down phase isinitiated by switching off the heating device when the door of thecooking compartment is opened. This measure has an additional safetyeffect since on the one hand, it protects the user for example fromexcessive thermal radiation when turning the food and on the other handprevents the heating device from remaining switched on if the door isunintentionally left open.

An exemplary embodiment of the invention is explained in detailhereinafter with reference to the drawings. In the figures:

FIG. 1 is a schematic diagram of a cooking device according to theinvention and

FIG. 2 is a schematic temperature-time curve of an exemplary cookingprocess.

FIG. 1 shows a cooking device 1 according to the invention which isshown as a grilling device in the present exemplary embodiment. Thecooking device contains a housing 2 which surrounds a cookingcompartment 3 which is closed by a door 4. Provided in the cookingcompartment 3 is a usual heating device 5 in the form of a heating coilwhich is arranged on the ceiling 3 a of the cooking compartment 3. Alsoprovided are the usual temperature sensors, preferably in the rear areaof the cooking compartment 3 which are not shown in the drawing.

The cooking device 1 further contains a control system not shown whichcan be actuated by conventional control elements 6.

Connected to the control system is a switching contact 7, which is onlyshown schematically and which actuates the opening and closing of thedoor. The switching contact 7 is embodied so that it switches off theheating device 5 as soon as the door 4 is opened and releases theswitching on of the heating device 5 as soon as the door 4 is closed.

A cooking process will be explained in detail with reference to thetemperature-time curve in FIG. 2. FIG. 2 shows the profile of a grillingprocess as a preferred cooking process. The user places the food forgrilling in the cooking compartment 3 and selects the desired operatingmode “grilling” and/or the desired cooking temperature and/or thedesired cooking time by means of the control elements 6. After the door4 is closed, the heating device is switched on and heats the cookingcompartment 3 for the time t_(V). During this time t_(V), the heatingdevice 5 stays switched on; the side of the food facing the heatingdevice is thus exposed to permanent thermal radiation and consequentlybrowns sufficiently. At the same time, the food pre-cooks. After thetime t_(V) has elapsed, the food must be turned. The user opens the door4 whereby the heating device 5 is switched off by the switching contact7. As a result, the cooking compartment 3 is not heated further and thetemperature drops to a reduced temperature T_(A) in the course of atemporary cooling phase t_(A). If the door 4 is closed again afterturning the food, switching on the heating device 5 is released again bymeans of the switching contact 7 so that the heating to thepre-determined food temperature T_(G) is continued in the time intervalt_(VS) with substantially the same curve gradient as in the range t_(V).In this way, the beginning of a regulating cycle t_(R) in which theheating device 5 is switched on and off in a clocked fashion to keep thetemperature constant between the cooking temperature T_(G) and a lowerswitching temperature T_(SU), is delayed. After turning the food, thesecond side of the food is thus exposed to the thermal radiation for alonger time than would be the case without the temporary cooling-downphase t_(A) and the food is browned better on the second side than wouldbe the case with the usual change between the thermal radiation andthermal convection with the usual length of the regulating cycle t_(R).The cooling-down phase t_(A) thus brings about a lengthening of theswitching-on time of the heating device after the cooling. Without thecooling-down phase t_(A) on the other hand, the heating-up phase wouldnot be interrupted or would substantially not be interrupted but wouldcontinue with the same angle of gradient as far as the cookingtemperature T_(G) and would then go over into the regulating phase as isindicated by the dot-dash profile II in FIG. 2.

It should be pointed out that the heating device 5 is designed asrelatively powerful especially for grill devices and the temperaturesensors are usually so remote from the door that they cannot beinfluenced by the user so that opening the door 4 for turning the foodwith the heating device 5 continuing to run brings about a slightlowering of the temperature but this lowering is not sufficient tosignificantly increase the switching-on time of the heating device afterturning and thus positively influence the degree of browning.

It is important for the efficiency of the invention that the temperaturewithin the temporary cooling-down phase t_(A) is reduced to a reducedtemperature T_(A) which is lower than the lower switching temperatureT_(SU). On the other hand, the temporal arrangement of the temporarycooling-down phase t_(A) can be applied to any point on the curve, i.e.,it can be introduced for example only in the regulating cycle t_(R) andinterrupt this.

The following table shows the effect of lengthening the cooling-downphase on the radiation time during the grilling of a steak.

Grilling steaks Grilling without door steaks with Duration contact doorcontact First side 10 minutes Heater on for Heater on for 10 minutes 10minutes Turning: about 30 Heater is Heater off seconds still on Secondside 5 minutes Heater on for Heater on for 2 minutes 3 min 40 sec Heateroff Heater off for 3 minutes for 1 min 10 sec

In a modification of the exemplary embodiment shown it is furtherpossible to incorporate the temporary cooling-down phase in a cookingprogram, for example, by stopping the heating device from being switchedon again after the temperature has fallen below the lower switchingtemperature, after first reaching the cooking temperature until thetemperature has fallen sufficiently far below the lower switchingtemperature or has been actively lowered so that an extended radiationtime of the heating device is then required.

The invention is preferably applied to grilling appliances or grillingdevices but can be used wherever good browning with short cooking timesand/or a safety function (by coupling with the door opening) isimportant.

1. A method for controlling a cooking process in a closed cookingcompartment of a cooking appliance, comprising: a heating device forheating the cooking compartment, said heating device being operable toapply radiant heat to an item in said cooking compartment; thetemperature in said cooking compartment is set to a desired heatingtemperature (TG) for the food in a cooking process; said heating deviceis switched on and off in a temperature regulating cycle once apre-determined switching temperature has been reached in said cookingcompartment during said cooking process to thereby ensure that thetemperature in said cooking compartment is between an upper limitcooking temperature and a lower limit cooking temperature; thetemperature during said cooking process is then reduced from apredetermined temperature below the upper cooking limit temperature overthe course of a temporary cooling-down phase (tA) in said cookingcompartment such that the temperature in said cooking compartmenteventually decreases below the lower limit cooking temperature; and thetemperature during said cooking process then is increased again during asubsequent heating-up phase (tVS) in said cooking compartment to raisethe temperature in said cooking compartment from a temperature below thelower limit cooking temperature to a temperature between the upper limitcooking temperature and the lower limit cooking temperature.
 2. Themethod according to claim 1, including said temporary cooling-down phase(tA) is brought about by an unscheduled switch-off of said heatingdevice relative to said regulating cycle.
 3. The method according toclaim 2, including said heating device is switched off when opening saidcooking compartment.
 4. The method according to claim 1, including saidtemporary cooling-down phase (tA) is introduced shortly before reachingsaid cooking temperature (TG).
 5. The method according to claim 1,including said temporary cooling-down phase (tA) is introduced when saidfood is turned.
 6. The method according to claim 5, including saidheating device is switched off when opening said cooking compartment toturn said food introducing said temporary cooling-down phase (tA).
 7. Acooking device, comprising: a cooking compartment in which an item canbe placed to be heated; a heating device for heating an item that hasbeen placed in said cooking compartment, said heating device beingoperable to apply radiant heat to the item; a door for accessing saidcooking compartment, said door being movable between an open position inwhich access can be had to said cooking compartment and a closedposition in which access to said cooking compartment is prevented; atemperature sensor for sensing the temperature in said cookingcompartment; and a control assembly operatively connected to saidtemperature sensor and operable to cyclically turn on said heatingdevice and turn off said heating device to thereby ensure that thetemperature in said cooking compartment is between an upper limitcooking temperature and a lower limit cooking temperature, said controlassembly being operable, when the temperature in said cookingcompartment eventually decreases along a path of increasingly lowertemperatures as a result of said heating device being in a turned offcondition, to turn on again said heating device during such a decreaseof the temperature in said cooking compartment along a path ofincreasing lower temperatures before the temperature in said cookingcompartment decreases below the lower limit cooking temperature, saidcontrol assembly controlling the turning on and the turning off of saidheating device in a cyclic manner to thereby ensure that the temperaturein said cooking compartment is between the upper limit cookingtemperature and the lower limit cooking temperature, and said controlassembly being operable to turn off said heating element upon theoccurrence of a predetermined temperature below the upper cooking limittemperature, said control assembly being operable, during a temporarycooling-down phase (tA), to maintain said heating element in a turnedoff status following an occurrence of a predetermined temperature belowthe upper cooking limit temperature such that the temperature in saidcooking compartment eventually decreases below the lower limit cookingtemperature, and said control assembly being operable to substantiallycontinuously maintain said heating element in its turned on conditionduring a subsequent heating-up phase (tVS) following a temporarycooling-down phase (tA) to raise the temperature in said cookingcompartment from a temperature below the lower limit cooking temperatureto a temperature between the upper limit cooking temperature and thelower limit cooking temperature.
 8. The cooking device according toclaim 7, including a switching contact engageable and activated by saiddoor in at least one of an open or a closed position, said switchingcontact being operatively connected to said control assembly and saidcontrol assembly being operable, when said heating element has alreadybeen in a turned on condition during a cooking process and saidswitching contact has indicated that said door has been opened, tomaintain said heating element in a turned off status in a predeterminedheating element turn-off event such that during a temporary cooling-downphase (tA) ensures and the temperature in said cooking compartmenteventually decreases below the lower limit cooking temperature.
 9. Thedevice according to claim 7, including a switching contact engageableand activated by said door in at least one of an open or a closedposition, said switching contact being operatively connected to saidcontrol assembly and said control assembly being operable, in responseto a signal from said switching contact that said door has been closedafter said heating element has already been in a turned on conditionduring a cooking process and said switching contact has alreadyindicated that said door has been opened and a temporary cooling-downphase (tA) has elapsed, to substantially continuously maintain saidheating element in its turned on condition during a heating-up phase(tVS) to raise the temperature in said cooking compartment from atemperature below the lower limit cooking temperature to a temperaturebetween the upper limit cooking temperature and the lower limit cookingtemperature.